High School

Find all real solutions of the polynomial equation. Enter your answers as a comma-separated list.

[tex]x^4 + 10x^3 + 24x^2 - 19x - 70 = 0[/tex]

Answer :

We start with the polynomial equation

[tex]$$
x^4 + 10x^3 + 24x^2 - 19x - 70 = 0.
$$[/tex]

Step 1. Factor the polynomial

Notice that the polynomial factors into

[tex]$$
(x + 2)(x + 5)(x^2 + 3x - 7) = 0.
$$[/tex]

Step 2. Set each factor equal to zero

We have three factors. Setting each factor equal to zero gives:

1. [tex]$$x + 2 = 0 \quad \Longrightarrow \quad x = -2.$$[/tex]
2. [tex]$$x + 5 = 0 \quad \Longrightarrow \quad x = -5.$$[/tex]
3. [tex]$$x^2 + 3x - 7 = 0.$$[/tex]

Step 3. Solve the quadratic equation

To solve the quadratic equation

[tex]$$
x^2 + 3x - 7 = 0,
$$[/tex]

we use the quadratic formula:

[tex]$$
x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a},
$$[/tex]

where [tex]$a=1$[/tex], [tex]$b=3$[/tex], and [tex]$c=-7$[/tex]. This gives:

[tex]$$
x = \frac{-3 \pm \sqrt{3^2 - 4(1)(-7)}}{2(1)} = \frac{-3 \pm \sqrt{9 + 28}}{2} = \frac{-3 \pm \sqrt{37}}{2}.
$$[/tex]

Thus, the quadratic yields two real roots:

[tex]$$
x = \frac{-3 + \sqrt{37}}{2} \quad \text{and} \quad x = \frac{-3 - \sqrt{37}}{2}.
$$[/tex]

Step 4. Write the complete list of solutions

The real solutions of the original polynomial equation are:

[tex]$$
\boxed{-2,\ -5,\ \frac{-3+\sqrt{37}}{2},\ \frac{-3-\sqrt{37}}{2}}.
$$[/tex]

These are all the real roots of the equation.